The present invention generally relates to a coupling device for attaching flexible tubular members to relatively rigid tubular structures and, more particularly is concerned with a product and method for securing a rubber air sleeve to parts of an adjustable air shock absorber, in a fluid-tight manner.
It has been common practice in vehicle leveling systems that function to maintain a predetermined height relationship between the chassis of a vehicle and its axle assemblies, to utilize one or more auxiliary fluid suspension components, i.e. adjustable air shock absorbers, to assist in the load-carrying capacity along with the vehicle springs. When a load has been added to the vehicle chassis the shock absorbers operate to supplement the load carrying capacity of the springs to return the vehicle chassis to a desired height relationship with respect to the axle assembly. When the load is removed from the vehicle, the springs and the shock absorbers co-act to cause the chassis to rise above the desired height relationship which requires that the pressurized fluid be exhausted from the shock absorbers.
Current shock absorbers are basically piston cylinder devices. Due to the hostile environment in which a shock absorber operates, most shock absorbers come with a protective dirt shield which keeps foreign material from the critical piston, cylinder workings. Between the dirt shield and the outer surface of the cylinder there exists an air gap which is sealed at its open end opposite to its mounting end. This seal may be accomplished by attaching a rubber air sleeve to both the dirt shield and the cylinder. The rubber sleeve provides a flexible, rolling diaphragm which is flexible for movement and at the same time fluid-tight.
Attaching this rubber air sleeve to the dirt shield and the cylinder is the subject of the present invention. Attaching any kind of hose or tube to other members to form a reliable fluid-tight coupling has presented problems for many years. Two basic problems are axial pull off (which is simply the separation of the hose or tube from the member) and pressure or vacuum sealing of a confined media such as air or water. Most methods for accomplishing this today usually consist of one of three varieties. They are adjustable hose clamp assemblies, crimped on ferrules, and attachments that screw on by the use of threads. These methods can provide an effective way of attaching a hose or tube to a member, but they tend to be troublesome from the standpoint of providing a reliable and lasting seal. Further, it is the nature of these attaching methods to produce high, localized stresses which cause early failure.
A member having a conical shape (diamond shapes have also been used) in combination with a frusta-conical locking sleeve have been used as a means to attach a hose. Generally, the hose is thrust over the large diameter portion of the cone and seated about the reverse tapered portion of the cone. This type of hose coupling has not been totally reliable and is not often used commercially. When a hose is thick or its material is stiff and unyielding, the outer sleeve has not worked well to exert adequate pressure on the hose. Improvements were made to this type of connection by modifying the locking sleeve with threads or springs. However, it has been found that the modifications need not be made to the sleeve but to the conical shaped member. The angle of taper of the conical shaped member is particularly important because the mechanical advantage of the locking sleeve capability decreases with increasing angle.
It is desirable to provide a coupling wherein a threadless locking sleeve could be easily set or engaged by hand or machine, which would eliminate the possible need for torquing the locking sleeve. With a proper angle range only very rudimentary means of preventing tube or hose pull off or sleeve securement are required.
It is, therefore, a primary object of the present invention to provide a new and improved means for securing a flexible, rolling diaphragm to a dirt shield and inner cylinder of an air-adjustable shock absorber wherein the connection is made using smooth surfaces and a compressive friction fit that does not rely on threads, crimps, adjustable clamping assemblies. Further, the connection includes a frusta-conical shaped lock sleeve which fits over the tapered ends of the dust shield and inner cylinder of the shock absorber. The angles of the tapers of the dirt shield and the inner cylinder are between one-half degree to four degrees per side and symmetrical about the central, longitudinal axis. The angle of taper on the lock sleeve is slightly less than the angle of taper of the dirt shield or inner cylinder. This specific angle range produces locking and sealing results that make the use of threads, springs, etc. no longer necessary to achieve the same reliability. Selection of the special angle range resists any relative movement between the sleeve, flexible tube, and the shield and/or cylinder that could loosen the mechanical lock on the reverse taper or disrupt the pressure sealing integrity of the attachment. Such a configuration allows the use of a very simple locking sleeve to assure that the sleeve remains positioned on the hose or tube, and that the hose or tube remains in position on the shield and/or cylinder. The final connection may be accomplished by hand setting of the locking sleeve, or by mechanical means.
If the angle defining the sealing portion is greater than the above noted specific range, very minor distortions of wall thickness will result in greater loss of sealing. Angles larger than those specified herein are believed to cause a more rapid deterioration of sealing. Also, larger angles require more distortion of the hose or tube material. Deterioration of the tube or hose material results in more rapid loss of sealing. In commercial use, attaching methods that are not reliable, regardless of cost, are not used. The use of the special angle range results in an improvement in the reliability of the attachment that is sufficient to allow commercial utilization.
Accordingly, there is provided herein a coupling device which includes a frusta-conical locking sleeve and a tapered end of a member which cooperate to resist pull off as well as having resistance to temperature changes, resistance to vibration changes, and resistance to mechanical forces that tend to push or pull on the tube or hose in a manner that unlocks the lock sleeve or encourages leaking. The interaction of these factors generally stems from the fact that the hose or tube is flexible and will exhibit resonances of mechanical motion.
The foregoing and other advantages will become more apparent when viewed in light of the accompanying drawings and the following detailed description.